The present invention relates to a drill. More particularly this invention concerns a chuck for a drill.
A standard drill chuck comprises a chuck body centered on and rotatable about an axis and formed with a plurality of angled guides spaced about the axis and each holding a respective jaw. Rear edges of the jaws have rows of teeth meshing with an internal screwthread of a tightening sleeve that can be rotated in one direction to advance the jaws axially and bring them together radially so as to grip a tool and in the opposite direction to separate the jaws and release the tool. Means may be provided to lock the tightening sleeve to prevent unwanted loosening of the chuck.
As a rule the chuck body is formed with an axially rearwardly open threaded bore into which fits an externally threaded spindle of a drive unit. The two parts are screwed together under substantial torque so that the chuck stays solidly mounted even under the considerable angular forces that it is subjected to in normal use. Frequently a radial set screw is fitted to the body and engages the spindle to angularly lock the parts together even more solidly.
Thus it is in theory possible to remove and replace the chuck, but this operation often is extremely difficult since over time the chuck body and drill spindle become frozen together. Thus changing a standard chuck as describe above with, for instance, a collet chuck or some sort of special-duty chuck is not practical, and normally not something easily carried out in the field.
It is therefore an object of the present invention to provide an improved drill chuck.
Another object is the provision of such an improved drill chuck which overcomes the above-given disadvantages, that is which can easily be removed from and replaced on a drill spindle.
A drill has according to the invention a drive spindle centered on and rotatable about a spindle axis and formed centered on the axis with an axially forwardly open socket of noncircular section and with at least one radially throughgoing passage open radially inward into the socket. A chuck body has a stem of noncircular section complementary to that of the socket, fixed to the chuck body, and extending along a stem axis from the chuck body. The stem is formed with a radially outwardly open recess. A locking element is radially displaceable in the passage between an inner position projecting radially inward into the socket and an outer position clear of the socket and projecting radially outward from the spindle. The stem is fittable to the socket with its recess aligned with the passage. A collar is formed with an inner surface closely juxtaposed with an outside surface of the spindle and with a radially inwardly open recess. The collar is axially displaceable on the spindle between a locked position with its inner surface pressing the element into the inner position and an unlocked position with its recess level with the element and the element movable into the outer position engaged in the collar recess.
Thus with this system simply shifting the collar in to the unlocked position allows the chuck to be taken off the spindle. The chuck can be changed, for instance a three-jaw chuck can be swapped with a collet chuck or a hex chuck. The changeover is simple so it can be done easily in the field. Nonetheless the mounted chuck is axially and rotationally solidly fixed on the drill spindle. In addition it is possible to use several different chucks for tools of different diameters on the same drill unit, for instance a half-inch and quarter-inch chuck can both be used.
The chuck body according to the invention is formed with a rotation-symmetrical surface portion and the spindle is formed with a complementary surface portion that snugly engages the surface portion of the body when the stem is fitted in the socket. In this case the chuck-body surface portion is a cylindrical inner surface centered on the stem axis and the spindle surface portion is a cylindrical outer surface centered on the spindle axis. Alternately the socket is formed with a rotation-symmetrical surface portion centered on the spindle axis and the stem is formed with a complementary surface portion that snugly engages the surface portion of the socket when the stem is fitted in the socket. Here the socket surface portion is a cylindrical inner surface centered on the spindle axis and the stem surface portion is a cylindrical outer surface centered on the stem axis. In both systems the chuck body is thus accurately centered on the drill spindle so that the tool or workpiece held by the chuck will be rotated accurately about the spindle axis.
In addition in accordance with the invention the spindle and chuck body are formed with respective axially engageable planar faces respectively perpendicular to the spindle and stem axes. More particularly the spindle has an outer end formed with the respective planar face or the stem has an outer end formed with the respective planar face and the socket has a floor formed with the planar face of the spindle. In this manner axial forces are also transmitted from the spindle to the chuck body.
The stem and socket are of polygonal section, normally hexagonal. This ensures excellent transmission of torque from the spindle to the chuck. Furthermore when the hex socket conforms to the standard hex drive size it is possible to directly chuck hex-shaft tools in the drill spindle, without using a chuck.
For most secure axial holding of the chuck on the spindle, the spindle is formed with a plurality of the passages each receiving a respective one of the locking elements and the recess of the stem is a radially outwardly open groove. The locking elements are balls. Thus there are several locations at which the spindle is secured to the chuck-body stem.
To prevent inadvertent disconnection of the chuck from the drill unit, a spring is braced between the spindle and the collar urging the collar into the locked position. Normally the locked position is axially forward of the unlocked position so the collar has to be pulled back to free the chuck.
The chuck body according to the invention is formed with a plurality of angled axially forwardly open guides each receiving a respective jaw. A tightening ring rotatable on the body has a screwthread meshing with the jaws.
To facilitate removal of the chuck a knockout rod is axially displaceable in the spindle and axially engageable with the stem. A spring urges the knockout rod outward against the stem. In this arrangement a second locking element is radially engageable with the knockout rod and with the collar. The second locking element is movable out of engagement with the knockout rod on displacement of the collar into the unlocked position. More particularly the spindle is formed with a second radially extending passage level with the knockout rod and holding the second locking element. The knockout rod is formed with a radially outwardly open recess in which the second element is radially engageable in the locked position of the collar. Thus pulling back the collar simultaneously frees the chuck-body stem and the knockout rod, causing the chuck to be ejected from the spindle.
To allow retrofit of the system of this invention to an existing drill unit with a threaded spindle, an outer port forming the socket is threaded to an inner part fixed on the drill unit.